The present invention relates generally to semiconductor integrated circuit (IC) devices, and more particularly to an IC device having a textured, rigid member overlying at least a portion of the active area of the IC.
As semiconductor IC bars increase in size, the packaging of the bars becomes more important in determining the integrity and reliability of the completed device. One problem associated with large bars, particularly those encapsulated in plastic, is the thermal expansion stress exerted on the bar by the package. The plastic and the bar and bar pad expand and contract at different rates, which can cause a shear force at the periphery of the bar sufficient to crack or otherwise damage ball bonds, or to disturb metal lines on the bar surface. This is particularly evident during temperature cycling of the completed device.
Another problem encountered in semiconductor IC devices, for example high density memory devices, is that of alpha particle radiation. It is known that alpha particles penetrating a memory device can alter the charge stored in the memory cells and thus destroy the data stored in the device. One method of preventing this is to include an alpha shield overlying the active area of the device. One such shield is a polyimide tape affixed by an adhesive to the surface of the IC. Alternatively, a polyimide film may be formed on the surface of the IC and cured in situ prior to encapsulation. An important disadvantage of polyimide, however, is its tendency to absorb moisture. Thus, particular care must be taken to form the film or to affix the tape in a moisture-free ambient.